1. Field of the Invention
The present invention relates to the field of balloon catheters, and in particular to a method and apparatus for accurate positioning of a dual balloon catheter.
2. Background Art
Balloon catheters are frequently used to impart axial or radial force to the interior of vessels in the body. However, prior art balloon catheters are difficult to initially position precisely, and precise positioning can be difficult to maintain as radial or axial forces are applied. Further, it is frequently impossible, due to the flexible nature of the catheter, to impart axial forces in more than one direction. This problem can be better understood by a review of balloon catheters.
Balloon Catheters
Balloon catheters are used for a variety of medical treatments. The ability to feed the flexible catheter through vessels in the body and, then, inflate a balloon portion of the catheter provides medical practitioners with the ability to impart radial or axial force from within a vessel of the body. Balloon catheters are frequently used to place stents. Another frequent use is to shear away obstructions from vessel walls (e.g. plaque on artery walls). Yet another use of balloon catheters is to enclose a region of a vessel between two balloons of the catheter and, then, introduce a treatment fluid into the enclosed region. Still another use is removing kidney stones by expanding the uterine wall and enabling the stone to move more readily out of the body.
Prior art balloon catheters share a common drawback: their accuracy is limited by the elasticity of the artery and its supporting structures. Since the artery and support structure can typically stretch up to 10% longitudinally, it is difficult to accurately place a balloon. It is especially difficult when attempting to position a balloon in a one millimeter long region using a one meter catheter (typical dimensions in some procedures).
Prior art balloon catheters are also prone to “watermelon seeding”, a type of positioning error commonly seen when dilating in-stent restenosis. This error occurs when a partially expanded balloon slips forcefully in the axial direction through the stationary embedded stent, similar to the manner in which a watermelon seed can be launched between pressed fingers.
A further drawback of balloon catheters is encountered when attempting to apply axial force. Prior art balloon catheters can only exert axial shearing forces when pulled in a retrograde fashion. This limitation is due to the fact that the flexible catheter system buckles when pushed. Thus, a balloon catheter is analogous to a string attached to a weight. The string can exert a force on a weight when pulled but not when pushed.
Prior Art Balloon Catheters
An example of a prior art balloon catheter is found in U.S. Pat. No. 4,295,464 issued to Shihata. The patent is directed to a catheter for removing ureteral stones having two treatment balloons. A first treatment balloon is positioned and inflated to provide increasing outward radial force to the inner walls of the ureter immediately below the position of the arrested stone. This expands the inner walls to the extent that the diameter between the walls at that point is larger than the diameter of the stone. The second treatment balloon is inflated and imparts a downward (retrograde) pressure to dislodge the stone. However, because both balloons are used as treatment balloons, the efficiency of the device suffers from the same precise position problem common to other balloon catheters. Additionally, the device is unable to impart axial sheering force in anything other than a retrograde direction.
Another example of a prior art balloon catheter is found in U.S. Pat. No. 5,074,845 issued to Miraki. The patent is directed to a catheter having a balloon that has an anchoring portion, a waste and a dilation portion. The waste is formed by heat treating a portion of the balloon so that the waste separates the anchoring portion from the dilation portion. The balloon is positioned near an occlusion and inflated so that the anchoring portion immobilizes the balloon. Then, the dilation portion extends through the occlusion site as the balloon inflates and eventually dilates the occluded area. However, the anchoring portion of the balloon must still be precisely positioned, so the catheter suffers from the same precise position problem common to other balloon catheters. Additionally, the device is unable to impart axial sheering force.
A similar balloon catheter is described in U.S. Pat. No. 5,458,573 issued to Summers and directed to a catheter with two treatment balloons. The first balloon is used to impart radial force upon a treatment area. The second balloon is smaller than the first balloon and is used to widen narrow treatment areas so that the catheter and first balloon may he advanced. The second balloon may also be used to trap freed obstructions (e.g., a loosened blood clot) during extraction of the catheter by keeping the second balloon inflated during extraction. This catheter also has the positioning and axial force limitations common to prior art balloon catheters.
Another similar balloon catheter is found in U.S. Pat. No. 4,990,139 issued to Jang and directed to a catheter with two treatment balloons. The first balloon is used to impart radial force upon a treatment area. The second balloon is larger than the first balloon and is used to widen the treatment area further. Similarly, a third, even larger balloon could be used. However, the additional treatment balloons do not eliminate or reduce the positioning and axial force limitations common to prior art balloon catheters.
Another balloon catheter is described in U.S. Pat. No. 5,788,708 issued to Hegde and directed to a catheter with multiple treatment balloons. The balloons are used to dilate vessel walls and place stents without the use of multiple, single balloon catheters._However, the additional treatment balloons do not eliminate or reduce the positioning and axial force limitations common to prior art balloon catheters.
A similar balloon catheter is found in U.S. Pat. No. 5,320,605 issued to Sahota is directed to a catheter with multiple treatment balloons. The balloons are at a fixed distance from each other and may be operated independently. The use of multiple smaller treatment balloons rather than a single, long treatment balloon enables the catheter to treat areas that are not easily accessible by single balloon catheters. While the multiple treatment balloons make maneuvering through turns in a vessel more efficient, they do not eliminate or reduce the positioning and axial force limitations common to prior art balloon catheters.
Yet another example of a prior art balloon catheter is found in U.S. Pat. No. 5,423,745 issued to Todd. The patent is directed to a catheter for introducing liquid into a body passageway. The catheter of Todd has an immobilizing balloon, which may have retention enhancements such as protruberances. Additionally, the catheter of Todd also has a sealing balloon used to enclose a portion of the body passageway between the immobilizing balloon and the sealing balloon. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
A similar balloon catheter is described in U.S. Pat. No. 5,919,163 issued to Glickman and directed to a catheter for creating an operating area within a body passageway. The catheter of Glickman has two sealing balloons, and an operating area is formed between the balloons upon inflation. Fluid may be introduced to the operating area, and the distance between the balloons is adjustable. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Additional similar balloon catheters are found in U.S. Pat. No. 4,911,163 issued to Fina, U.S. Pat. No. 5,342,306 issued to Don Michael, U.S. Pat. No. 4,445,892 issued to Hussein, all being directed to catheters for creating an operating area within a body passageway. The catheters of the patents have two sealing balloons, and an operating area is formed between the balloons upon inflation. Fluid may be introduced to the operating area, and if an obstruction is dislodged by the treatment, one or both of the balloons can be maintained as inflated during withdrawal of the catheter to aid in extracting the dislodged obstruction. However, the catheters are subject to the same positioning and axial force limitations common to other balloon catheters.
More balloon catheters are described in U.S. Pat. No. 6,156,005 and U.S. Pat. No. 5,423,742, both issued to Theron and directed to catheters having an occlusion balloon and a treatment balloon. The occlusion balloon is inflated to prevent fragments from escaping during treatment. The treatment balloon is inflated to dilate a treatment stent. However, the catheters are subject to the same positioning and axial force limitations common to other balloon catheters.
Still another balloon catheter is described in U.S. Pat. No. 5,868,708 issued to Hart and directed to a catheter having a balloon that can be inflated into predetermined configurations. A mesh around the balloon controls the configuration of the inflated balloon. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Additional balloon catheters are found in U.S. Pat. No. 5,653,690 issued to Booth, U.S. Pat. No. 5,487,730 and U.S. Pat. No. 5,720,726 issued to Marcadis, and U.S. Pat. No. 4,927,412 issued to Menasche, all directed to catheters for introducing liquid into the heart having a single retention (or immobilizing) balloon. The retention balloon can have retention enhancements such as sloping spikes or barbed protrusions. However, the catheters are subject to the same positioning and axial force limitations common to other balloon catheters.
Another balloon catheter is found in U.S. Pat. No. 3,448,739 issued to Stark and directed to a catheter having a single balloon. The balloon may be used either as an occlusion balloon during introduction of fluids through the catheter or as a treatment balloon used to impart radial force against a passage wall. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Still another balloon catheter is described in U.S. Pat. No. 6,258,099 B1 issued to Mareiro and directed to a catheter having a single balloon. The balloon has protrusions to prevent unwanted movement of an expandable, implantable medical device such as a stent during delivery and deployment. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Yet another balloon catheter is described in U.S. Pat. No. 5,019,075 issued to Spears and directed to a catheter having a single balloon. A heated fluid is pumped through the balloon upon inflation to create a smooth channel upon deflation to reduce abrupt arterial closure or gradual restenosis. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Another balloon catheter is found in U.S. Pat. No. 5,968,012 issued to Ren and directed to a catheter having a single balloon. The catheter has a length compensator to compensate for balloon movement. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Still another balloon catheter is described in U.S. Pat. No. 5,868,703 issued to Bertolero and directed to a catheter having a single balloon. Channels in the catheter enable delivery of blood and other fluids during treatment or cardiac surgery. The balloon has protrusions to help secure its position. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Yet another balloon catheter is described in U.S. Pat. No. 5,179,961 issued to Littleford is directed to a catheter having a positioning balloon. The positioning balloon is inflated to center the catheter as it is maneuvered through winding and potentially occluded passageways. When the catheter is centered, it is less likely to become stuck. However, the catheter is subject to the same positioning and axial force limitations common to other balloon catheters.
Further examples of balloon catheters are described in U.S. Pat. No. 5,616,149 issued to Barath (directed to a catheter with a treatment balloon having cutting edges for making lateral cuts in the vessel wall); U.S. Pat. No. 5,693,014 and U.S. Pat. No. 5,746,745, both issued to Abele (directed to an angioplasty balloon wherein when not inflated, the balloon surface has a low coefficient of friction, but, when the balloon is inflated, a second surface is exposed that has a higher coefficient of friction); U.S. Pat. No. 4,292,974 issued to Fogarty (directed to a catheter with a treatment balloon, wherein the balloon is twisted when not inflated so as to enable the balloon to fit into smaller spaces); U.S. Pat. No. 4,351,341 issued to Goldberg (directed to a catheter having a lumen formed from a coil); U.S. Pat. No. 5,250,070 issued to Parodi (directed to an angioplasty balloon, wherein the balloon is irregularly formed, having a plurality of grooves and radially projecting parts between the grooves, and wherein the balloon is used to impart radial force to a treatment area in a less traumatic manner than other designs); U.S. Pat. No. 6,018,857 issued to Duffy (directed to a method and apparatus for mounting a stent onto a catheter balloon); and U.S. Pat. No. 4,733,665 issued to Palmaz (directed to an expandable intraluminal vascular graft, wherein the graft is expanded using a catheter balloon). However, all of these catheters are subject to the same positioning and axial force limitations common to other balloon catheters.